Conventionally, there has been used a DC circuit breaker which is installed in an electric circuit to allow or prevent supply of a DC power to a load (see, e.g., Japanese Patent Application Publication No. H11-339605 (paragraphs [0016] to [0034], and FIGS. 1 to 4)). This DC circuit breaker includes a pair of fixed contactors respectively having fixed contact points and a pair of movable contactors respective having movable contact points which selectively contact with the fixed contact points of the fixed contactors. The contact points of both contactors can be brought into contact with or separated from each other by operating a handle provided at a front surface of a base.
In the DC circuit breaker described in Japanese Patent Application Publication No. H11-339605, a contact unit including the fixed contactors and the movable contactors does not have a sealed structure. Therefore, the contact points may be oxidized or sulfided by gas in the atmosphere, or contact reliability between the contact points may decrease due to adhesion of foreign materials to the contact points. Accordingly, a location where it can be used is limited.
Further, in a circuit which requires a higher DC voltage, arc occurring between contact points increases. Thus, the number of arc-extinguishing grits for extinguishing the arc needs to be increased, and a space therefor is needed. As a consequence, the breaker may be scaled up.
Moreover, the arc occurring between the contact points may be discharged to the outside of the main body by magnetic force. In that case, however, a space for discharging the arc is required, so that other components cannot be installed close to the breaker.